"Social democracy" was always just a Maoist bugbear in the Bernie context. The standard in 2016 was much 'lower,' in the sense that the demands were specific and manageable. Nobody thinks you can turn the US into Sweden, but we should at least beat Mexico on healthcare.
That the 'movement' got bogged down by the impossible demands of the strivers was less a historical necessity (the blackpill line) than a tragic contingency, albeit perhaps a foreseeable one given the recent history of the American left.